\section{Main Data Types and Data Files}

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There are three main types of entities in GraspIt!. The first one is a
\textbf{Body}, which is characterized by having some geometry (a
shape), a transform (its position) and material properties (such as
friction coefficient). The second one is a \textbf{Robot}, which is
comprised of multiple Bodies (such as its links) as well as
information on kinematics, actuation, etc. Finally, a \textbf{World}
groups together instances of the other classes and places them in the
correct positions relative to each other. Each of these classes has
its own data file format, which GraspIt! can load (but, with the
exception of the World, not save to). We will detail all of them in
this section.

